A new dual-behavior FSS resonator for waveguide filter with multiple attenuation poles

This paper proposes a new element shape of frequency selective surface (FSS) for designing a waveguide filter with multiple attenuation poles like an elliptic-function filter. The FSS is a dual-behavior resonator by the combination of the aperture-type and the patch-type FSSs. Introducing such FSSs can realize high skirt selectivity by utilizing anti-resonances (full reflection) in stopbands at both sides of passband in addition to resonance (full transmission) in a passband. To design the waveguide filter, the resonant characteristics for various geometrical parameters of the FSS are investigated. As a design example, we demonstrate the bandpass filter with 4% bandwidth at the center frequency 10 GHz. The effectiveness of the waveguide filter with the FSSs proposed here is validated by good agreement between the calculated and the measured results.